Resource constraints on soil microbial metabolism critically influence biogeochemical cycling and ecosystem functioning. However, the drivers and mechanisms underlying soil microbial resource limitation, particularly across broad spatial scales, remain incompletely understood. Here, we investigated patterns of soil microbial resource limitation using enzymatic stoichiometry in subtropical forests developed on two contrasting lithologies (limestone and clastic rock) in southwest China, and explored linkages with climatic, plant, microbial traits (i.e., biomass and community composition measured via qPCR), and soil geochemical factors. Activities of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes and their stoichiometric ratios differed significantly between lithologies. Vector analysis revealed that soil microbes in clastic rock forests experienced greater C and P limitation, whereas those in limestone forests were more N-limited. Random forest and structural equation modeling identified lithology, rather than climate, as the primary factor regulating microbial resource limitation within this subtropical region, primarily through its influence on soil geochemistry and microbial traits. These findings underscore the predominant role of lithology in shaping soil microbial resource limitation in subtropical forests, with significant implications for understanding nutrient cycling and carbon sequestration in these globally important ecosystems.

Soil organic carbon (SOC) dynamics are a critical regulator of the global carbon cycle and climate feedbacks. Afforestation is widely recognized as a key nature-based climate solution for enhancing SOC sequestration, but its impact on the dynamics of soil lignin and microbial necromass carbon, and their roles in particulate (POC) and mineral-associated (MAOC) organic carbon accumulation remains poorly understood. This study selected 14 pairs of maize fields and adjacent plantation forests in a karst region of southwest China, where soils are predominantly calcareous. By combining lignin phenols and amino sugars as biomarkers with multiple biotic and abiotic soil variables, the mechanisms governing soil POC and MAOC accumulation upon afforestation were investigated. Afforestation substantially promoted soil carbon sequestration, resulting in 265% and 136% increases in POC and MAOC, respectively, compared with maize fields. Soil microbial necromass carbon increased by 224% in POC and 96% in MAOC, exceeding lignin increments (100% in POC; 66% in MAOC) upon afforestation. Structural equation modelling demonstrated three synergistic pathways of POC and MAOC following afforestation, that is, enhancing lignin accumulation via increased plant residue input and reduced lignin oxidation; promoting microbial necromass carbon accumulation driven by rising microbial biomass; and strengthening Ca-mediated mineral protection. However, multiple lines of evidence corroborated that microbial necromass carbon, not lignin, was the dominant driver of both POC and MAOC accumulation upon afforestation. Synthesis and applications. Our study refines the conventional dual-pathway framework of organic carbon formation by focusing on calcareous soils, and propose that microbial necromass, as a common precursor of soil POC and MAOC, drives their coupled accumulation following afforestation on cropland. This finding emphasizes the necessity of integrating microbial-mediated pathways for both POC and MAOC sequestration into Earth systems models, conducive to improving the predictive accuracy of SOC dynamics under global changes. Furthermore, afforestation strategies in karst regions should also prioritize tree species traits that promote soil microbial anabolism (e.g. high root exudation) and calcium retention to maximize the regional carbon sink potential. (sic)(sic)(sic)(sic)(sic)(SOC)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(POC)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(MAOC)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic))(sic)14(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)POC(sic)MAOC(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic), POC(sic)MAOC(sic)(sic)(sic)(sic)(sic)265%(sic)136%.(sic)(sic)(sic), POC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)224%, MAOC(sic)(sic)(sic)(sic)96%, (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(POC(sic)(sic)100%, MAOC(sic)(sic)66%).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)POC(sic)MAOC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic);(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic);(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)POC(sic)MAOC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)"(sic)(sic)(sic)"(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)POC(sic)MAOC(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)POC(sic)MAOC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)SOC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic)(sic))(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Predicting soil carbon dynamics under warming is constrained by limited understanding of microbial thermal adaptation, particularly whether microbial carbon use efficiency (CUE) can adapt to warming and how plant diversity modulates this response. Using soils from a natural tree species diversity gradient in a subtropical forest, we combined a 365-day laboratory incubation with regular substrate amendment and 18O-H2O labeling to quantify thermal responses of microbial respiration, growth, and CUE. High tree species diversity was associated with a strengthened compensatory thermal adaptation of microbial respiration and growth, effectively dampening their response to warming. Simultaneously, diversity promoted an enhanced thermal response of CUE, increasing microbial carbon retention capacity under warming. This dual regulation was mechanistically linked to a cascade of processes: higher tree species diversity was associated with lower soil organic matter stability (i.e., higher lability), minimizing bioenergetic costs of enzyme synthesis, facilitating a community-wide shift toward r-selected bacteria, and intensifying microbial competition as evidenced by network topology. Our findings reveal the potential of biodiversity to buffer soil carbon losses: conserving and restoring plant diversity can enhance soil capacity to mitigate climate change, both by reducing respiratory carbon losses and by increasing the potential for microbial carbon sequestration under warming.

Long-term fertilization profoundly influences soil health and agricultural sustainability, but its effects on ecosystem multifunctionality (EMF) in fragile karst agroecosystems remain poorly understood. In the karst regions of southwest China, inappropriate tillage and fertilization measures have triggered severe land degradation issues. We therefore conducted a 12-year experiment based on a maize-soybean rotation system in southwest China’s karst areas to identify effective fertilization strategies applicable in fragile karst agroecosystems. The experimental treatments comprised an unfertilized control (CK), mineral fertilizer (NPK) alone, and NPK combined with straw or cattle manure at low (LSNPK, LMNPK) and high (HSNPK, HMNPK) rates. We assessed the effect of constrasting fertilization strategies on crop productivity, soil organic carbon stability, microbial community structure, and EMF. All fertilization treatments increased combined maize and soybean productivity relative to CK, but their effects on soil health diverged markedly. Among the five fertilization treatments, HMNPK maximized the proportion of large macroaggregates (> 2000 µm) and the organic carbon concentration within them. HMNPK also elevated the chemical stability of soil organic carbon compared to CK and HSNPK. Phospholipid fatty acid and biomarker analyses revealed the highest microbial biomass and necromass carbon under HMNPK. Consequently, HMNPK yielded the highest EMF index, outperforming HSNPK and NPK. A nutrient management regime with high-rate manure input is an effective strategy for enhancing karst agroecosystem multifunctionality. This approach sustains high crop productivity while simultaneously improving soil structure, SOC stability, and microbial community abundance, thereby benefiting long-term agricultural sustainability.

Abstract Vegetation restoration is an important global strategy to enhance ecosystem resistance and promote soil organic carbon (SOC) sequestration. However, under this strategy, the mechanism underlying soil recalcitrant organic carbon (ROC) accumulation, particularly the relative contributions of plant‐ versus microbial‐derived carbon, remains insufficiently explored. Using a space‐for‐time substitution approach, we selected three land‐use types (cropland, shrubland and secondary forest) to represent a vegetation restoration chronosequence in karst regions of southwest China. We quantified soil lignin and microbial necromass carbon (MNC) by employing biomarker technologies (lignin phenols and amino sugars) and combined these measurements with ROC to assess relative contributions of plant versus microbial residues to stable SOC accumulation. Across the three land‐use types, ROC accounted for more than 60% of total SOC pool. Vegetation restoration significantly increased soil ROC content by 193%, indicating that this strategy improved SOC stability and benefited long‐term preservation of soil carbon. While both lignin and MNC contents significantly increased during vegetation restoration, MNC was identified as the key predictor of soil ROC accumulation. Soil MNC accumulation in shrublands and secondary forests was strongly associated with increased soil carbon and nitrogen availability and mineral protection (exchangeable calcium+magnesium and free and short‐range ordered iron+aluminium oxides). Concurrently, higher substrate availability and mineral protection also facilitated soil lignin preservation. Importantly, fungal and bacterial necromass contributed almost equally to ROC accumulation. This phenomenon likely stemmed from the improvement in soil pH during vegetation restoration, which alleviated acid stress on bacterial proliferation. Synthesis and applications : Our study expands the traditional lignin‐centric theoretical framework of carbon accumulation and emphasizes that the unique geochemical environment of karst regions facilitates a synchronous accumulation of bacterial and fungal necromass, jointly promoting stable SOC sequestration. We therefore propose that restoration strategies for karst‐degraded ecosystems should focus on fostering active soil microbial communities while introducing plant species that facilitate soil calcium enrichment to enhance microbial carbon sequestration potential and promote the long‐term preservation of SOC.

Afforestation is a primary nature-based strategy for climate change mitigation, yet its efficacy relies on the long-term persistence of sequestered soil organic carbon (SOC). Nevertheless, the molecular-level mechanisms governing this persistence remain understudied. Here, we investigated the impacts of afforestation on former maize fields after 20 years on soil organic matter (SOM) molecular composition and complexity in topsoil (0-15 cm) and subsoil (30-45 cm) in a subtropical karst region of southwest China, using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) coupled with network analysis. Afforestation significantly reshaped the topsoil SOM composition, driving a 160% increase in lignin-derived compounds and a 58% decrease in polysaccharides, reflecting the shift from crop residues to woody inputs. Afforestation significantly increased the molecular network complexity of SOM in both topsoil and subsoil, indicating the formation of a more intricate and interconnected web of organic compounds. Structural equation modeling revealed that afforestation's impact was indirect, primarily mediated by increased fine root biomass and enhanced organo-mineral interactions characteristic of the calcareous soil environment. Our findings provide compelling molecular-level evidence that afforestation in the karst region promotes SOC persistence not only by increasing carbon inputs but by building a more complex SOM architecture. This increased complexity, arising from the interplay between new plant-derived precursors and the strong protective capacity of the mineral matrix, represents a key mechanism for enhancing SOC persistence and validates afforestation as a potent ecological restoration tool in the karst regions.

AIMS:Soil-borne pathogens pose a significant threat to global agriculture. While certain soils naturally suppress disease, the complex interplay between different microbial kingdoms and their metabolic functions in orchestrating this suppression remains poorly understood. METHODS AND RESULTS:We integrated 16S/ITS/18S rRNA amplicon sequencing with nontargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics to elucidate the multikingdom microbial drivers and metabolic profiles of rhizosphere soils from healthy (HS) and diseased (DS) mulberry (Morus alba L.) orchards. The HS orchard, under long-term organic fertilization, exhibited strong disease suppression (12% incidence), whereas the DS orchard, under chemical fertilization, was highly susceptible (85% incidence) to wilt disease. The HS soils harbored a more complex and stable microbial co-occurrence network. This community was significantly enriched in putative beneficial taxa, including the bacteria Stenotrophomonas and Pseudomonas, the fungus Mortierella, and the predatory protist Colpoda. In contrast, the pathogen Fusarium was enriched in DS soils. Functional profiling predicted that the HS microbiome possessed a higher potential for antibiotic biosynthesis and stress tolerance. Metabolomic analysis revealed a striking divergence in metabolic pathways. DS plants mounted a massive but ineffective defense, characterized by the accumulation of phytoalexins. We identified a significant downregulation of the glycosylphosphatidylinositol-anchor biosynthesis pathway in DS soils, a fundamental process for anchoring functional proteins to the plant cell surface. CONCLUSIONS:Our findings reveal a novel pathogenic strategy of targeting host cell-surface architecture and the corresponding community-level defense mechanism.

Soil microbial carbon use efficiency (CUE), defined as the proportion of assimilated carbon allocated to microbial growth versus maintenance, is a key parameter regulating terrestrial soil organic carbon (SOC) storage. The response of CUE to climate change and its feedbacks profoundly affect global carbon cycle and soil carbon sequestration. At present, there are substantial uncertainties regarding the mechanisms underlying the responses of CUE to climate change and the ecological consequences. We synthesized research progress on soil microbial CUE over the past 20 years. First, we clarified the basic concept and computational approaches of CUE, and compared the principles, strengths, and limitations of three mainstream measurement techniques (isotope labeling method, stoichiometric model, and thermodynamic efficiency method). Second, we summarized the key biotic and abiotic factors influencing CUE. Focused on the mechanisms underlying the main and interactive effects of elevated atmospheric CO2 concentration, climate warming, and altered precipitation patterns on microbial CUE, and based on a "resource-cost trade-off" framework, we discussed the potential mechanisms underlying the heterogeneous responses of CUE across different ecosystems, and summarized the bottlenecks and challenges that still existed in current research regarding methodological standardization, the analysis of deep soil processes, the quantification of multi-factor interaction effects, and the application of CUE in earth system models (ESMs). We proposed an integrative research framework spanning from micro-scale metabolic mechanisms to macro-scale carbon cycling patterns, emphasizing the need for methodological innovation, multi-scale networked observations, and model-experiment integration, to thoroughly reveal the dynamics and adaptive mechanisms of CUE under climate change.

Soil organic nitrogen (SON) transformation is critical for global nutrient cycling and ecosystem productivity, yet how its responsiveness to climate change differs across diverse land use types remains poorly resolved. We measured gross protein depolymerization (GPD), microbial N growth, gross N mineralization (GNM) and microbial N use efficiency (NUE) in paired forest and cropland soils along a broad climatic gradient in subtropical China to quantify differential climate associations and identify governing biogeochemical controls. Forest soils exhibited substantially higher GPD (82%), microbial growth (132%) and NUE (26%) compared to adjacent croplands, while GNM rates were similar between land uses. Across the observed spatial climate gradient, SON transformations in forests showed strong positive co-variation with climate: GPD, Ngrowth and GNM increased with mean annual temperature (MAT) and mean annual precipitation (MAP) (slopes for MAT = 0.59, 0.84, 0.49; for MAP = 0.55, 0.62, 0.23), whereas NUE declined with both MAT and MAP (slopes = -0.68 and -0.63, respectively). In contrast, cropland SON processes were largely insensitive to MAT and MAP except that Ngrowth and NUE increased modestly with MAT. Mechanistic analyses indicated contrasting regulatory pathways: in forests, climatic effects were transmitted mainly through mineral-enzyme interactions (e.g. iron/aluminium oxides modulating protease activity) and resource stoichiometry (e.g. dissolved organic carbon:available phosphorus ratio), with GPD tightly coupled to Ngrowth and GNM and acting as a rate-limiting step. In croplands, temperature effects were largely indirect, operating through base cation to iron/aluminium-oxide ratios, resource availability (free amino acids, carbon:N ratio), and microbial functional gene abundances, yielding a decoupling of depolymerization from downstream processes. These results show that land use strongly modulates the climate-associated responsiveness of SON transformations: forest soils are more vulnerable to climate-driven changes in N cycling than intensively managed croplands. Our findings have implications for land-use-specific management and for improving predictions of N dynamics under global change.Read the free for this article on the Journal blog. (sic)(sic)(sic)(sic)(sic)(SON)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), SON(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(GPD),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(Ngrowth),(sic)(sic)(sic)(sic)(sic)(GNM)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(NUE)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)GPD (+82%),Ngrowth (+132%)(sic)NUE (+26%), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(GNM)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)SON(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):GPD,Ngrowth(sic)GNM(sic)(sic)(sic)(sic)(sic)(MAT)(sic)(sic)(sic)(sic)(sic)(MAP)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(MAT(sic)(sic)(sic)(sic)(sic)(sic)(sic)0.59,0.84,0.49;MAP(sic)(sic)(sic)(sic)(sic)(sic)(sic)0.55,0.62,0.23), (sic)NUE(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic) -0.68 (sic) -0.63).(sic)(sic), (sic)(sic)(sic)(sic)(sic)SON(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)Ngrowth(sic)NUE(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic))(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic))(sic)(sic);(sic)(sic)(sic)(sic)(sic), GPD(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)Ngrowth(sic)GNM(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)/(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic))(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Microbial respiration (Rm) and its temperature sensitivity play a crucial role in soil organic carbon (SOC) dynamics under climate change. Although vegetation restoration is considered an effective strategy to enhance SOC storage, the persistence of this carbon pool under warming depends on Rm responses. In addition, the effects of vegetation restoration on microbial respiration and its temperature sensitivity in karst regions remain unclear, and the mechanisms across different restoration modes have not been systematically investigated. We selected a representative karst region in southwestern China and examined three land-use types: cropland (CL), plantation forests on abandoned farmland (PF), and naturally regenerated secondary forests (SF), using a randomized block design. Soil samples were incubated under controlled laboratory conditions to measure cumulative microbial respiration and its temperature sensitivity. Natural restoration significantly increased microbial respiration, while artificial restoration enhanced the sensitivity of Rm to temperature. Vegetation restoration increased microbial respiration mainly through greater carbon input and elevated Rm sensitivity by reducing SOC mineral protection. Compared with artificial restoration, natural restoration increased SOC stocks but reduced the temperature sensitivity of SOC decomposition. Vegetation restoration exerts distinct effects on microbial respiration and its temperature sensitivity in karst regions. These findings highlight that different restoration modes influence SOC stability through contrasting mechanisms, providing guidance for climate-resilient land management.

Afforestation is crucial for soil organic carbon (SOC) sequestration, yet the depth-specific mechanisms, particularly the roles of lignin and microbial necromass carbon (MNC) in SOC accumulation, are not well elucidated. Understanding these processes is vital for optimizing carbon management strategies. To address this, we conducted a paired-site study in a subtropical karst region of Southwest China, comparing 14 maize fields with adjacent similar to 20-year-old plantation forests. Soil lignin, MNC, SOC, and related edaphic variables were quantified in topsoil (0-15 cm) and subsoil (30-45 cm) to determine the impacts of afforestation. Results showed that afforestation significantly increased SOC, lignin, and MNC in both soil layers. Topsoil lignin and MNC contents rose by 74.5% and 64.3% (P < 0.001), respectively. While subsoil SOC also increased, the relative importance of lignin and MNC to SOC accumulation was lower than in topsoil. Our analysis suggests that mineral protection, particularly by exchangeable calcium and magnesium, was the dominant SOC stabilization pathway, responsible for 45% of SOC variance in the subsoil. Our findings reveal distinct, depth-dependent pathways for SOC accumulation following afforestation: in topsoil, accumulation was primarily driven by biotic inputs, especially microbial necromass, while mineral protection, through mechanisms like cation bridging and aggregation, was crucial in subsoil. These insights advocate for depth-differentiated management, such as selecting tree species that enhance topsoil microbial activity and prioritizing sites with high mineral content for subsoil carbon stabilization, to maximize SOC sequestration following afforestation in the karst regions.

Nature-based climate solutions rely on the assumption that restoring plant diversity enhances soil organic carbon (SOC) sequestration. However, the persistence of SOC is threatened by the positive priming effects, where fresh plant carbon inputs accelerate the decomposition of native SOC. It remains unclear how increasing plant diversity impacts the soil priming effects. Here, using a natural tree species diversity gradient in a subtropical forest, we show that higher tree diversity was strongly associated with suppressed soil priming effects, attributable to reduced mineral protection of SOC and alleviated microbial energy limitation. Microbial community consequently shifts toward fast-growing specialists that outcompete decomposers of chemically complex carbon. Our study reveals that tree species diversity is a key regulator of SOC persistence and demonstrates that the biodiversity-driven priming suppression should be explicitly incorporated into nature-based climate solutions and Earth system models to reduce critical uncertainties in carbon cycle projections.

Abstract Plant species diversity (PSD) is known to enhance soil organic carbon (SOC) storage, but how it affects distinct SOC fractions, such as particulate (POC) and mineral-associated organic carbon (MAOC), remains unclear. We aimed to elucidate the mechanisms by which PSD regulates the accumulation of POC and MAOC, specifically by disentangling the biotic and abiotic drivers mediating these effects in a subtropical forest. We assessed the variations in surface soil characteristics (0-10 cm layer) and SOC physical fractions (specifically POC and MAOC), across a natural gradient of PSD in a representative subtropical forest in southwest China. POC content ranged from 8.37 to 87.6 g C kg−1 soil (mean: 31.3 ± 20.4 g C kg−1 soil), and MAOC content ranged from 17.6 to 61.0 g C kg−1 soil (mean: 33.2 ± 11.3 g C kg−1 soil). Increasing PSD significantly enhanced POC accumulation and marginally increased MAOC, resulting in a shift in SOC fractions toward a higher POC proportion. Higher PSD was associated with increased soil exchangeable Ca and Mg, which correlated with greater mineral protection of plant- and microbial-derived carbon compounds (e.g., lignin phenols and amino sugars), subsequently fostering the accumulation of both POC and MAOC. Our findings highlight the importance of mineral protection mechanisms, mediated by divalent cations, in regulating POC and MAOC accrual in subtropical forests. PSD indirectly influences SOC fraction dynamics through enhanced mineral stabilization of biologically derived carbon, underscoring the role of biogeochemical pathways in linking PSD to soil carbon storage.

The persistence of antibiotic resistance genes (ARGs) and pathogens during manure composting poses critical risks within the One Health framework. However, the ecological and metabolic mechanisms by which microbiome engineering disrupts the dissemination of these biohazards remain poorly understood. This study evaluated a thermophilic lignocellulose-degrading synthetic microbial community (SynCom, comprising Bacillus cereus, Achromobacter sp., Pseudomonas sp., Cladosporium sp., and Trichoderma harzianum) in mitigating these risks. KEGG analysis highlighted a pivotal metabolic reprogramming from a biofilm-dependent defense-survival model to an active motility-metabolism mode, characterized by depleted lipopolysaccharide biosynthesis and enriched flagellar assembly. This metabolic shift implies a fitness cost trade-off that physically restricts horizontal gene transfer (HGT) opportunities. Metagenomic analysis showed SynCom inoculation caused a transient ARG rebound followed by profound attenuation. While thermophilic hosts temporarily enriched specific ARGs, SynCom ultimately achieved a significant reduction in multidrug resistance genes and virulence factors by intensifying thermophilic fermentation. Mantel correlation analysis revealed the SynCom-driven rapid decrease in carbon/nitrogen ratio and enhanced humification were critical environmental drivers, restricting ARGs and alleviating co-selection pressure on metal resistance genes. Network analysis demonstrated SynCom induced a structural collapse of high-risk interactomes (reducing potential host-gene associations by 26.6%), effectively disrupting ARG and mobile genetic element connections by suppressing key recombinases (XerD, IntI1) and eliminating Pseudomonadota hub hosts. Consequently, deep bio-sanitization was achieved by synchronously eliminating high-risk pathogens (e.g., Pseudomonas aeruginosa), phytopathogens, and specific virulence factors. These findings indicate that SynCom provides a robust microbiome engineering strategy to disrupt the genetic dissemination of biohazards and ensure organic fertilizer biosafety.

Afforestation has been well documented to enhance soil organic carbon (SOC) pools. However, the capacity of soils to mitigate global warming depends critically on SOC persistence, which is fundamentally governed by the accumulation of non-labile SOC fractions following afforestation. Here, we employed physical fractionation of organic carbon via size/density separation. SOC and its two functionally distinct fractions, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), were quantified in corn-soybean rotation fields and pine plantation forests located in two geological backgrounds: clasolite and limestone areas in southwest Guangxi Province, China. The plantation forests were established in former corn-soybean fields 30-40 years ago. Bulk SOC and MAOC contents in croplands were 74.8% and 86.3% higher, respectively, in limestone areas than in clasolite areas, whereas SOC and its fractions in forests showed no significant differences between the two lithological types. In limestone areas, SOC, POC and MAOC did not differ significantly between croplands and forests, whereas in clasolite areas, these fractions increased by 41.3%, 139.1% and 37.7%, respectively, after afforestation. The proportions of MAOC in croplands constituted 95.7% and 94.0% of bulk SOC in limestone and clasolite areas, respectively, but were reduced by 4.9% and 4.5% following afforestation. These results suggest that afforestation reduces SOC stability by decreasing the proportion of MAOC. Incorporating the effects of afforestation on SOC stability into Earth system models is essential for improving predictions of climate-carbon cycle feedback, particularly given the potential prevalence of our observed pattern.

Glomalin-related soil protein (GRSP), a key biomolecule regulating soil organic carbon (SOC) dynamics, plays a critical role in promoting SOC storage and stabilization. However, its response to vegetation restoration in high-mineral karst ecosystems remains poorly understood. This study investigated the effects of vegetation restoration (cropland, shrubland, and secondary forest) on GRSP accumulation and its contribution to SOC in a karst region of southwest China. Vegetation restoration significantly increased SOC and total GRSP contents, with secondary forest exhibiting 211.2 % higher SOC and 55.3 % higher total GRSP compared to cropland. Conversely, total GRSP's contribution to SOC decreased by 50.3 % in the secondary forest relative to cropland, likely due to the "dilution effect" from increased plant-derived carbon inputs. Random forest modeling showed that soil minerals (e.g., exchangeable Ca/Mg) and labile nitrogen were key factors in regulating total GRSP accumulation. This study highlights the pivotal role of soil minerals in mediating GRSP accumulation during vegetation restoration, providing new insights into microbial-controlled carbon sequestration mechanisms in karst ecosystems. These findings are crucial for optimizing ecological restoration strategies to enhance long-term soil carbon storage in mineral-rich environments.

Clonal integration not only changes underground soil resources but also significantly influences the evolution of surface plant communities, which is crucial for karst vegetation restoration. This study measured the main nutrient indicators of Loropetalum chinense rhizosphere soil at different stages, and investigated the impact mode of clonal integration on the nutrient status of rhizosphere soil, as well as its influence on nutrient supply capacity during vegetation succession. From early to late stages, compared with non cloned plants, clonal integration leads to a decrease in carbon, nitrogen, and potassium content in the rhizosphere soil of the mother plant and ramets, while the content of available phosphorus in the soil increased. The C, C, and Nin the rhizosphere soil of plants undergoing clonal integration were higher than those in the rhizosphere soil of non-cloned plants. According to the GLM (Generalized Linear Model), clone integration was one of the key factors affecting the phosphorus content in rhizosphere soil. We further found that clonal integration alleviated the limitation of vegetation growth in karst areas to soil phosphorus.